In thermal dye sublimation printing, it is generally well known to render images by heating and pressing one or more donor materials such as a colorant (e.g., a dye) or other coating against a receiver medium having a colorant receiving layer. The heat is generally supplied by a thermal print head having an array of heating elements. The donor materials are typically provided in sized donor patches on a movable web known as a donor ribbon. The donor patches are organized on the ribbon into donor sets; each set containing all of the donor patches that are to be used to record an image on the receiver web. For full color images, multiple color dye patches can be used, such as yellow, magenta, and cyan donor dye patches. Arrangements of other color patches can be used in like fashion within a donor set. Additionally, each donor set can include an overcoat or sealant layer.
Thermal printers offer a wide range of advantages in photographic printing including the provision of truly continuous tone scale variation and the ability to deposit, as a part of the printing process a protective overcoat layer to protect the images formed thereby from mechanical and environmental damage. Accordingly, many photographic kiosks and home photo printers currently use thermal printing technology.
Some thermal printing systems are adapted to print on individual sheets of receiver media. Thermal printing systems that are used for large volume applications (e.g., photographic kiosks) commonly utilize roll-fed receiver media.
Conventionally, thermal printers have been adapted for producing single-sided images and have used receiver media having a colorant receiving layer coated on only one side of a substrate. There are a variety of applications (e.g., photo books and photo calendars) where it is desirable to print on both sides of the receiver media to provide double-sided images. Some prior art approaches for printing on both sides of the receiver media have utilized two printing stations, each including its own thermal print head and donor ribbon, one to print each side of the image. This adds significant cost and size to the thermal printer design. Other prior art approaches have utilized large and cumbersome mechanisms within the thermal printer to reposition the receiver media supply roll after the first-side image has been printed in order to print the second-side image. This approach also adds significant cost and size to the thermal printer design.
There remains a need in the art for a duplex thermal printer that is low-cost and compact.